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Iím a huge cryptocurrency / block-fad distractor but there are some cases where itís a useful tool. Of course I do believe any real implementations will be private and trust controlled. And proof of brute force work will be phased out.

Itís a tool that has specific uses. The gold rush right now is about trying to use it for every problem. Obviously that will crash and burn.

And that's assuming you solve the problems around transaction throughput and network availability. Which you won't.

Quantum computers around the corner? :3

Quantum computing chips aren't really designed to solve these kinds of problems. Their problems are more like "analyze every surface of this mountain range simultaneously and tell me the highest peak and lowest valley" or "find the most likely result of this economic situation".

Might they be used in the future to do cryptographic analysis? Probably, but I haven't seen that yet.

"Holy shit, I ask you to stop being autistic and you debate what autistic is." - spasm

It is absurd that we are capable of witnessing a 40,000 year old system of gender oppression begin to dissolve before our eyes yet still see the abolition of a 200 year old economic system as an unrealistic utopia.

Quantum computing chips aren't really designed to solve these kinds of problems. Their problems are more like "analyze every surface of this mountain range simultaneously and tell me the highest peak and lowest valley" or "find the most likely result of this economic situation".

Might they be used in the future to do cryptographic analysis? Probably, but I haven't seen that yet.

They will be useful for certain cryptographic work: Shor's algorithm dramatically improves the performance of integer factorization and finding (elliptic curve) discrete logarithms. Grover's algorithm improves the performance for breaking symmetric algorithms like block ciphers and hash functions (EG the double SHA256 used in Bitcoin, though this is less direct[1]). Grover's algorithm effectively halves the number of bits of effective security, so a 256-bit cipher would be as effective as a 128-bit cipher is today. Hash functions require more bits for security than block cipher primitives, so Bitcoin will probably be breakable by quantum computers if they are actually possible.

The "if they are actually possible" bit is important: they work at very small scales but the difficulty of building a general-purpose quantum computer* grows exponentially with the number of qbits needed. The connections decohere faster and faster as more qbits are added, such that beyond 10-15 qbits (the current record is 10) the system decoheres (can't be used for computation) so quickly that we can't measure it. Going to the fastest measurement systems possible (femtosecond lasers) would only add 1-2 more qbits, even if those measurement systems were appropriate for the task at hand (they aren't). Several hundred are needed for any practical attacks. I'd estimate we're at least 50 years away from a practical general purpose quantum computer, and that's likely to be the perpetual 50 years away of Fusion power.

* D-wave's "quantum computer" is not general purpose. It only does simulated annealing, which isn't relevant to cryptography in any way.

Quantum computing chips aren't really designed to solve these kinds of problems. Their problems are more like "analyze every surface of this mountain range simultaneously and tell me the highest peak and lowest valley" or "find the most likely result of this economic situation".

Might they be used in the future to do cryptographic analysis? Probably, but I haven't seen that yet.

They will be useful for certain cryptographic work: Shor's algorithm dramatically improves the performance of integer factorization and finding (elliptic curve) discrete logarithms. Grover's algorithm improves the performance for breaking symmetric algorithms like block ciphers and hash functions (EG the double SHA256 used in Bitcoin, though this is less direct[1]). Grover's algorithm effectively halves the number of bits of effective security, so a 256-bit cipher would be as effective as a 128-bit cipher is today. Hash functions require more bits for security than block cipher primitives, so Bitcoin will probably be breakable by quantum computers if they are actually possible.

The "if they are actually possible" bit is important: they work at very small scales but the difficulty of building a general-purpose quantum computer* grows exponentially with the number of qbits needed. The connections decohere faster and faster as more qbits are added, such that beyond 10-15 qbits (the current record is 10) the system decoheres (can't be used for computation) so quickly that we can't measure it. Going to the fastest measurement systems possible (femtosecond lasers) would only add 1-2 more qbits, even if those measurement systems were appropriate for the task at hand (they aren't). Several hundred are needed for any practical attacks. I'd estimate we're at least 50 years away from a practical general purpose quantum computer, and that's likely to be the perpetual 50 years away of Fusion power.

* D-wave's "quantum computer" is not general purpose. It only does simulated annealing, which isn't relevant to cryptography in any way.

* D-wave's "quantum computer" is not general purpose. It only does simulated annealing, which isn't relevant to cryptography in any way.

This is the one quantum computer I am somewhat familiar with, as I work in the factory making their chips. They have 2000-qbit chips, btw.

Yes, but those qbits aren't all entangled with one another. Sticking tons of SQUIDs or other qbit devices on a chip is easy. I wouldn't say that what D-wave has done is easy, but it's vastly, VASTLY easier than maintaining coherence with large numbers of entangled qbits. It's like the difference between learning to make fire and figuring out how to smelt steel.

A different solution space as it were. Advances in what is being called deep learning provide a more likely pathway to solve problems like that, and so far that doesn't get any meaningful increase from quantum computing, over a general improvement from evolutionary new software architectures a broader shift to something like that would bring about.

lmao, ancap's wet dream is going to come true and completely crush their vision of utopia

Originally Posted by Paul Mason

It is absurd that we are capable of witnessing a 40,000 year old system of gender oppression begin to dissolve before our eyes yet still see the abolition of a 200 year old economic system as an unrealistic utopia.